This invention relates to extensible outriggers for truck cranes and the like, and particularly to an improved mounting arrangement and other features relating to the vertical cylinders of such outriggers.
Truck cranes and similar machines are commonly provided with extensible outriggers comprising a single or multi-section horizontal beam that is extended and retracted by a horizontal cylinder, and a vertical cylinder that is mounted on the outer end of the beam and is provided with a stabilizing float. Particularly in truck cranes where travel width is a problem because of highway restrictions, it is desirable to have self-storing floats that can be pivoted to vertical storage positions alongside the vertical cylinders--this invention contemplates an arrangement in which the float is cammed to its stored position upon retraction of the vertical cylinder. Conventionally, vertical outrigger cylinders have a radial mounting flange at the rod end of the cylinder casing and are mounted by bolting this flange to the underside of the beam. This typical mounting arrangement, however, presents a number of major problems. For example, since the cylinder flange is substantially larger than the outside diameter of the casing, and since the float must clear the flange when in its stored position, the overall retracted length of the assembly is undesirably increased. Further, the wide flange presents clearance problems in the usual situation in which there are parallel and adjacent beam housings for the opposite sides of the machine, since the two housings must be moved farther apart to provide clearance for the flanges, which increases the width and weight of the outrigger beam assembly. Still further, since the cylinder flange is bolted to the underside of the beam with the casing extending through the beam, and since the beam is relatively close to the ground, removal of the vertical cylinder for repair or replacement is very difficult; it is usually necessary either to remove the outer beam section entirely or else dig a hole deep enough to allow the vertical cylinder to be removed from underneath the beam. Further, the flange defines and restricts the vertical elevation of the vertical cylinder, which in turn defines the ground clearance for the float as it moves to and when it is in the stored position; this problem might be resolved by raising the bottom wall of the beam to put the flange higher, but this is undesirable from the standpoint of beam strength and would put the flange at a level where there could be a clearance problem with the horizontal beam cylinder.
Attempts have been made to mount vertical outrigger cylinders by means of pins rather than flanges, but these have generally resulted in eccentric loading or presented other problems.
The noted clearance problems with a typical flange tend to multiply to the point where it is difficult or impossible to design a fully satisfactory outrigger assembly. It is, for example, generally accepted that the optimum extended spread, relative to the width of the machine, for dual, opposed outriggers with single section beams is approximately 2:1 (the spread for an 8 foot machine would be 16 feet) and the optimum ratio where the beams have two sections is 2.5:1 (20 feet for an eight foot machine); other design considerations generally prevent exceeding these ratios. With the typical flange mounting, however, and particularly with self-storing floats, it is virtually impossible even to reach these ratios while still providing a retracted length which does not exceed the width of the machine.
There are also design problems with regard to self-storing outrigger floats. Where, as contemplated in this invention, the float is cammed to its stored position upon retraction of the vertical cylinder, for proper operation it is necessary to provide some means to insure that the float is properly aligned relative to the camming member, which means must not create clearance or other additional problems or interfere with the freedom of the float to adjust for uneven ground conditions.